U.S. patent number 4,009,814 [Application Number 05/611,064] was granted by the patent office on 1977-03-01 for web accumulator.
This patent grant is currently assigned to Scott Paper Company. Invention is credited to Balbir Singh.
United States Patent |
4,009,814 |
Singh |
March 1, 1977 |
Web accumulator
Abstract
Disclosed is a web accumulator for accumulating and discharging
a reserve portion of a continuous web passing through the
accumulator. The accumulator, which is particularly useful for
handling weak webs such as sanitary or tissue paper, includes first
and second sets of rotatably mounted web rolls, each of which is
partially wrapped by the web when the web is looped alternately
from a roll of the first set to a roll of the second set in
consecutive order. The second set of web rolls is mounted for
movement towards and away from the first set of web rolls to
discharge and accumulate the reserve portion of the web, and the
accumulator preferably includes drive means separate from the web
for driving each web roll at the speed of the web passing over it
at all times including when it is accumulating or discharging. The
drive means is preferably provided by a drive pulley operably
connected to each web roll and preferably having the same size as
its respective web roll, an endless flexible belt engaging the
drive pulleys in the same sequence that the web engages the web
rolls, inlet drive means for rotating the first web roll, exit
drive means for rotating the exit web roll, and take-up means for
taking up and releasing slack in the drive belt occurring when the
second set of rolls moves towards or away from the first set.
Inventors: |
Singh; Balbir (Media, PA) |
Assignee: |
Scott Paper Company
(Philadelphia, PA)
|
Family
ID: |
24447482 |
Appl.
No.: |
05/611,064 |
Filed: |
September 8, 1975 |
Current U.S.
Class: |
226/113;
226/118.2 |
Current CPC
Class: |
B65H
20/34 (20130101); B65H 2301/522 (20130101); B65H
2403/72 (20130101); B65H 2555/24 (20130101) |
Current International
Class: |
B65H
20/30 (20060101); B65H 20/34 (20060101); B65H
017/42 () |
Field of
Search: |
;226/91,113,114,118,119 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Schacher; Richard A.
Attorney, Agent or Firm: Yamaoka; Joseph H. Foley; William
J.
Claims
I claim:
1. A web accumulator for accumulating and discharging a reserve
portion of a continuous web passing through the accumulator in
order to compensate for the difference between an inlet speed and
an outlet speed of the web, the accumulator comprising:
first and second sets of rotatably mounted web rolls, each of which
is partially wrapped by the web when the web is looped alternately
from a roll of the first set to a roll of the second set in
consecutive order, the second set of rolls being mounted for
movement with respect to the first set of rolls;
means responsive to the inlet and outlet speed of the web for
moving the second set of web rolls towards the first set of web
rolls to discharge the reserve portion of the web when the outlet
speed exceeds the inlet speed and for moving the second set of web
rolls away from the first set of web rolls to accumulate the
reserve portion of the web; and
web roll drive means separate from the web for rotating each roll
at the speed of the web portion in contact with it when discharging
and accumulating the reserve portion of the web.
2. The accumulator described in claim 1, wherein the web roll drive
means comprises:
a plurality of drive pulleys providing a drive pulley operatively
connected to each web roll for rotating its respective web roll,
each drive pulley having a pitch diameter equal to the diameter of
the web roll it drives;
an endless flexible drive belt operatively engaging the drive
pulleys in the same sequence as the web engages the web roll;
and
drive belt take-up means for taking up and releasing slack in the
drive belt occurring when the second set of web rolls moves towards
or away from the first set of web rolls.
3. A web accumulator for accumulating and discharging a reserve
portion of a continuous web passing through the accumulator, the
accumulator comprising:
first and second sets of rotatably mounted web rolls, each of which
is partially wrapped by the web when the web is looped alternately
from a roll of the first set to a roll of the second set in
consecutive order, the second set of rolls being mounted for
movement with respect to the first set of rolls;
means for moving the second set of web rolls towards and away from
the first set of web rolls to discharge and accumulate the reserve
portion of the web;
a plurality of drive pulleys providing a drive pulley operatively
connected to each web roll for rotating its respective web roll,
each drive pulley having a pitch diameter equal to the diameter of
the web roll it drives;
an endless flexible drive belt operatively engaging the drive
pulleys in the same sequence as the web engages the web roll;
drive belt take-up means for taking up and releasing slack in the
drive belt occurring when the second set of web rolls moves towards
or away from the first set of web rolls;
exit drive means for rotating the last web roll in the accumulator
at an exit speed; and
inlet drive means for rotating the first web roll in the
accumulator at an inlet speed.
4. A web accumulator described in claim 3, further including a
carriage mounted for movement towards and away from the first set
of web rolls and upon which the second set of web rolls is mounted,
whereby the carriage and the second set of web rolls are moved
towards the first set of web rolls when the exit speed is greater
than the inlet speed, and the accumulator further includes means
for moving the carriage away from the first set of web rolls when
the inlet speed is greater than the exit speed.
5. A web accumulator for accumulating and discharging a reserve
portion of a continuous web passing through the accumulator, the
accumulator comprising:
first and second sets of rotatably mounted web rolls, each of which
is partially wrapped by the web when the web is looped alternately
from a roll of the first set to a roll of the second set in
consecutive order;
exit drive means for rotating the last web roll in the accumulator
at an exit speed;
inlet drive means for rotating the first web roll in the
accumulator at an inlet speed;
a carriage mounted for movement towards and away from the first set
of web rolls and upon which the second set of web rolls is mounted;
and
carriage drive means separate from the web and operatively
connected to the exit drive means and inlet drive means for moving
the carriage towards and away from the first set of web rolls in
response to the difference in exit speed and inlet speed, whereby
the web is accumulated when the inlet speed is greater than the
exit speed and the web is discharged when the exit speed is greater
than the inlet speed.
6. The web accumulator described in claim 5, wherein the carriage
drive means comprises a flexible belt driven by the exit drive
means and the inlet drive means and following the same path as the
web passing through the accumulator.
7. A web accumulator for accumulating and discharging a reserve
portion of a continuous web passing through the accumulator, the
accumulator comprising:
first and second sets of rotatably mounted web rolls, each of which
is partially wrapped by the web when the web is wound alternately
from a roll of the first set to a roll of the second set in
consecutive order;
mounting means upon which the second set of web rolls is mounted
for movement towards the first set of web rolls in a discharge
direction to discharge the reserve portion of the web and for
movement away from the first set of web rolls to accumulate the
reserve portion of the web, the mounting means permitting the
second set of web rolls to move in the discharge direction past the
first set of web rolls to a threading position for threading the
web through the accumulator;
a plurality of drive pulleys providing a drive pulley operatively
connected to each of the web rolls for rotating its respective web
roll;
an endless flexible drive belt operatively engaging the drive
pulleys in the same sequence as the web engages the web roll;
drive belt take-up means for taking up and releasing slack in the
drive belt occurring when the second set of web rolls moves towards
and away from the first set of web rolls; and
means for positioning each drive pulley connected to one set of the
web rolls in a position which is not passed by the web rolls of the
other set when the second set of web rolls is moved into the
threading position, whereby the drive belt remains engaged with the
drive pulleys.
8. A web accumulator for accumulating and discharging a reserve
portion of a continuous web passing through the accumulator, the
accumulator comprising:
first and second sets of rotatably mounted web rolls, each of which
is partially wrapped by the web when the web is wound alternately
from a roll of the first set to a roll of the second set in
consecutive order;
exit drive means for rotating the last web roll in the accumulator
at an exit speed;
inlet drive means for rotating the first web roll in the
accumulator at an exit speed;
inlet drive means for rotating the first web roll in the
accumulator at an inlet speed;
a carriage mounted for movement towards and away from the first set
of web rolls and upon which the second set of web rolls is
mounted;
a plurality of drive pulleys providing a drive pulley operatively
connected to each web roll for rotating its respective web roll,
each drive pulley having a pitch diameter equal to the diameter of
the web roll it drives;
a plurality of take-up pulleys rotatably mounted in a mirrored
relationship to the drive pulleys; and
an endless flexible drive belt operatively engaging the drive
pulleys in the same sequence as the web engages the web rolls and
extending into operable engagement with the take-up pulleys in a
mirrored relationship to its engagement with the drive pulleys,
whereby a difference between the inlet and outlet speeds of the
accumulator causes movement of the carriage to accumulate or
discharge the reserve portion of the web and drives each web roll
at the speed of the web portion in contact with it.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to web accumulators for accumulating and
discharging a reserve portion of a continuous web passing through
the accumulator to enable continuous operation of processing
stations on either or both sides of the accumulator when the speed
of the web moving through the processing stations temporarily
varies between the two stations. The invention is particularly
useful for handling weak webs, such as sanitary or tissue
paper.
2. Description of the Prior Art
In many processing operations involving continuous lengths of web
material, there are temporary differences in operating speeds
between two adjacent operating stations. For example, in the
manufacture of sanitary or tissue paper products, it is common to
unwind paper from a large parent roll and conduct it through a
finished or converting operation. In such operations, it is often
desirable to rewind the paper into rewound rolls of a specific size
which are not necessarily the same size as the parent rolls,
resulting in either the parent roll being depleted before the
rewound roll is completed or the rewound roll being completed
before the parent roll is depleted. The operation is then
maintained by splicing a new parent roll to the end of the paper or
by starting a new rewound roll, either of which would require
halting the operation unless a reserve portion of the web had been
accumulated for continued operation of the rewound roll or a
reserve portion of the web can be accumulated while a new rewound
roll is prepared. This problem is quite old and is generally solved
through use of web accumulators.
The typical accumulator for such uses is the festooning type, such
as that disclosed in U.S. Pat. No. 3,645,463. Festooning type
accumulators typically consist of a set of fixed web rolls and a
set of movable web rolls which are moved towards and away from the
fixed rolls. The web is looped alternately from a roll of the first
set to a roll of the second set in consecutive order. The movable
set of rolls are typically attached to a single carriage which is
moved away from the fixed rolls for accumulating a reserved portion
of the web and moved toward the fixed rolls for discharging the
accumulated reserve portion of the web. The amount of web which can
be accumulated is generally quite large for the size of the
apparatus, being equal to twice the movement distance of the
carriage times the number of rolls mounted on the carriage.
Examples of prior art web accumulators are disclosed in U.S. Pat.
Nos. 1,261,056; 3,693,860; 3,698,613; 3,700,157; 3,734,370;
3,743,153; and Re. 27,139.
A number of shortcomings exist in the web accumulators of the prior
art, particularly for use with weak webs like sanitary or tissue
paper. For example, most employ freely rotatable rolls which obtain
their rotational force from the web moving across them. Since the
portion of the web passing about each roll will be moving at a
different speed than the portions of the web passing about other
rolls during accumulating or discharging, the use of the web itself
to rotate the rolls has been thought in the past to be the only
practicable way to drive the rolls. Many of the prior art
accumulators are used for accumulating metal strips and other
strong web materials where the strong web materials can be depended
upon to rotate the rolls. However, weak webs such as sanitary or
tissue paper cannot always be relied upon to drive the rolls since
the paper is inclined to break. Another common shortcoming of the
typical prior art accumulators is their dependence upon the web
material to drive the carriage towards the fixed rolls. Again, weak
web materials such as sanitary or tissue paper cannot always be
relied upon for transmitting carriage driving forces.
It is therefore an object of the invention to provide a web
accumulator in which the web is festooned over rolls and each roll
is driven by means separate from the web at the speed of the web in
contact with it at all times including when it is accumulating or
discharging. It is a further object of the invention to provide a
web accumulator in which the web is festooned over rolls and in
which one set of rolls is driven towards and away from the other
set of rolls by drive means separate from the web in response to
any difference in speed between the web entering the accumulator
and the web leaving the accumulator. And it is a further object of
the invention in its preferred embodiment to provide a web
accumulator which accomplishes both of the above objects in a
single apparatus.
SUMMARY OF THE INVENTION
These and other objects are accomplished by the apparatus of the
invention which includes first and second sets of rotatably mounted
web rolls, each of which is partially wrapped by a web when the web
is festooned about the rolls by being wound alternately from a roll
of the first set to a roll of the second set in consecutive order.
The second set of rolls is mounted, preferably to a carriage, for
movement towards and away from the first set of rolls. Each web
roll is preferably provided with a drive pulley operably connected
to it and having a pitch diameter equal to the diameter of the web
roll it drives. In the preferred embodiment the accumulator further
includes a plurality of take-up pulleys rotatably mounted in a
mirrored relationship to the drive pulleys with one set of the
take-up pulleys mounted on the carriage. An endless flexible drive
belt operably engages the drive pulleys in the same sequence as the
web engages the web rolls and continues into operable engagement
with the take-up pulleys in a mirrored relationship to its
engagement with the drive pulleys.
The first web roll in the accumulator is preferably driven by inlet
drive means at the inlet speed of the web entering the accumulator,
and the last web roll in the accumulator is preferably driven by
exit drive means at the exit speed of the web leaving the
accumulator. The inlet drive pulley and exit drive pulley being
operably connected to their respective web rolls are also driven at
the inlet speed and exit speed, respectively. When the exit speed
is faster than the inlet speed, the drive belt responds to the
speed difference by decreasing its festooned length about the drive
pulleys and thereby moves the carriage towards the first set of web
rolls and discharges the reserve portion of the web. When the web
exit speed is slower than the web inlet speed, the drive belt
responds to the speed difference by decreasing its festooned length
about the take-up pulleys and thereby moves the carriage away from
the first set of web rolls and accumulates a reserve portion of the
web. When the carriage is being moved either away from or towards
the first set of web rolls, each web roll is automatically driven
at a different speed by the drive belt to match the speed of the
web in contact with the roll.
The invention in its preferred embodiment automatically and
instantaneously accumulates and discharges a reserve portion of the
web in response to speed differences between the inlet and the
outlet of the web passing through the accumulator, and it
automatically drives each web roll at the speed of the web in
contact with it, all without depending upon the force being
provided by the web itself. Thus the invention is particularly
advantageous for use with weak webs such as sanitary or tissue
paper.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side elevational view of the web accumulator of the
invention in schematic form.
FIG. 2 is an isometric view of the accumulator illustrated in FIG.
1.
FIG. 3 is a side elevation view of the accumulator illustrated in
FIG. 1 modified to have an easy-thread feature.
FIG. 4 is a side elevation view of a portion of the apparatus
illustrated in FIG. 3, but shown with the carriage in a different
position.
FIG. 5 is a schematic illustration of the accumulator of the
invention in an embodiment which permits a greater accumulation of
web reserve.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIGS. 1 and 2, the accumulator of the invention is
indicated generally by the numeral 11. It consists of a first set
of web rolls 12-16 rotatably mounted near the bottom of frame 17
and a second set of web rolls 18-21 rotatably mounted on a carriage
22. The carriage 22 is mounted for movement towards and away from
the first set of web rolls 12-16 along conventional guide means
such as guide members 23 on both sides of frame 17.
A continuous web 24 is passed through the accumulator 11 by
partially wrapping about inlet web roll 12, looping up over web
roll 18, back down and about web roll 13, and so forth until it
wraps about exit web roll 16 and passes from the accumulator 11.
The web 24 is shown being unwound from a parent roll 25 through
such means as a driving belt 26 in contact with the periphery of
the parent roll 25. Inlet drive means interconnects driving belt 26
with inlet web roll 12 to drive inlet roll 12 at the same surface
speed as web 24 is unwound from parent roll 25. Inlet drive means
is provided by reversing gears 5 and 6, chain drive 27 and
sprockets 7 and 9. Reversing gear 5 is mounted on a common shaft
with driving belt 4, and reversing gear 6 is mounted on a common
shaft with sprocket 7. Sprocket 9 is mounted on a common shaft with
inlet web roll 12. Driving belt 26 and inlet drive means are both
driven by conventional motor means or other drive means (not
illustrated).
The web 24 is driven by conventional S-rolls 28 and 29 after it
leaves accumulator 11. After passing through S-rolls 28 and 29, Web
24 continues into operational station 8, which can be a rewinder or
any other processing equipment. Exit drive means operably
interconnect S-rolls 28 and 29 with exit web roll 16 to drive exit
web roll 16 at the same surface speed as web 24 is driven by
S-rolls 28 and 29. Exit drive means is provided by drive chain 30
and sprockets 10 and 29. Sprocket 10 is mounted on a common shaft
with exit web roll 16, and sprocket 29 is mounted on a common shaft
with S-roll 29. Conventional motor means or other drive means (not
illustrated) drives S-rolls 28 and 29 at the same web surface speed
as the web speed through operation station 28.
Each web roll 12-16 and 18-21 is operably connected to a drive
sprocket 31-39, by each being mounted to a shaft common to its
respective drive sprocket. Each drive sprocket 31-39 has a pitch
diameter equal to the roll diameter of its respective web roll
12-16 and 18-21. A continuous or endless chain 40 is looped about
drive sprockets 31-39 in the same manner as web 24 is looped about
web rolls 12-16 and 18-21. Inlet drive means drives inlet drive
sprocket 31 and drive chain 40 at the inlet web speed. Exit drive
means drives exit drive sprocket 35 and drive chain 40 at the same
speed as the exit web speed.
The accumulator 11 further includes first and second sets of
take-up sprockets 41-49 positioned in a mirrored relationship to
the drive sprockets 31-39. Thus, the first set of take-up sprockets
41-45 are rotatably mounted to the upper part of frame 17 in a
mirrored relationship to the first set of drive sprockets 31-35,
and the second set of take-up sprockets 46-49 are rotatably mounted
to carriage 22 in a mirrored relationship to the second set of
drive sprockets 36-39.
When the accumulator 11 is in operation and the parent roll 25 is
being unwound at the same surface speed as web 24 is passing into
operation station 8, all of the web rolls 12-16 and 18-21 rotate at
the same speed and the carriage remains stationary. If the exit
speed of web 24 becomes faster than the inlet speed of web 24,
drive chain 40 will be driven faster by exit drive sprocket 35 than
by inlet drive sprocket 31. Accordingly, the festooned length of
drive chain 40 about the take-up sprockets 12-16 and 18-21 (along
the route taken by web 24) will be shortened, resulting in carriage
22 being pulled downwardly towards the first set of web rolls
12-16. At the same time, the festooned length of drive chain 40
about the take-up sprockets 41-49 will be lengthened, resulting in
the carriage 22 being permitted to move downwardly. Since drive
chain 40 is looped to and from carriage 22 and the first set of
take-up sprockets 41-45 the same number of times it is looped to
and from carriage 22 and the first set of drive sprockets 31-35,
carriage 22 will be pulled downwardly at the same speed that it is
permitted to move downwardly. The same operation occurs in reverse
when the exit speed of web 24 becomes slower than the inlet speed
of web 24. Thus, any difference between the speed of the web 24
entering and the speed of the web 24 leaving the accumulator
automatically causes the accumulator to either accumulate or
discharge a reserve portion of the web 24. Since inlet web roll 2
and exit web roll 16 are each driven at the same speed as their
respective operation stations preceding and following the
accumulator 11, any difference in speed between the two operation
stations, including halting one while continuing the other, causes
the accumulator 11 to automatically accumulate or discharge the
required amount of reserve portion of the web 24 to continue
operations. Of course, it shall be clear that only a limited amount
of web can be accumulated and discharged, so operating speed
differences can be accommodated only temporarily.
During discharge of the reserve portion of web 24 from the
accumulator 11, carriage 22 will be moving downwardly towards the
first set of web rolls 12-16 and the web 24 will be moving at a
different speed over each web roll 12-16 and 18-21. To illustrate
the speed differences, consider the exit speed of the web to be
V.sub.e and the inlet speed of the web to be V.sub.i. The carriage
speed can be assumed to be V.sub.c. V.sub.c is equal to (V.sub.e
-V.sub.i)/8, and the web speed at each web roll will be the
following:
The speed of web 24 at each web roll 12-16 and 18-21 will be the
same as the inlet speed of the web 24, V.sub.i, and the exit speed
of the web 24, V.sub.e, just prior to beginning discharge of the
reserve portion of the web 24. When discharging begins the sudden
change in speed of the web over each web roll 12-16 and 18-21
cannot be tolerated by weak webs if the web rolls obtain their
drive force from the web, as they conventionally do in the prior
arts. However, in the present invention drive chain 40, being
subjected to the same speed changes as the web 24, imparts the
drive force to the web rolls and is easily capable of tolerating
the speed changes. Furthermore, drive chain 40 will automatically
and instantaneously change the speed of each web roll to match the
speed of the portion of web 24 passing over it. At the same time,
drive chain 40, will automatically and instantaneously move
carriage 22 up or down to accumulate or discharge the required
length of reserve web to match the speed difference between the web
inlet and exit.
FIGS. 3 and 4 illustrate an alternative embodiment of the invention
with an easy thread feature. Features having the same indicating
numerals as features in other figures are the same. The embodiment
of FIGS. 3 and 4 is like that of FIG. 1 with the exceptions set
forth in the following description. Carriage 122 is designed to
permit the second set of web rolls 18-21 to extend below the first
set of web rolls 12-16 when carriage 122 is in its lowermost or
threading position (illustrated in FIG. 3). When carriage 122 is in
the threading position, web 24 can be threaded straight through the
accumulator 11, as illustrated in FIG. 3. After threading, carriage
122 is raised, moving the second set of web rolls 18-21 above the
first set of web rolls 12-16, as illustrated in FIG. 4, and
automatically causing web 24 to loop alternately about a roll in
the first set of web rolls 12-16 and a roll in the second set of
web rolls 18-21 in consecutive order.
In the easy thread embodiment illustrated in FIGS. 3 and 4, each of
the first set of drive sprockets 31-35 is rotatably mounted below
its respective web roll 12-16 and in a position lower than the
threading position of second set of web rolls 18-21. In this
arrangement, endless drive chain 40 will not fall from the first
set of drive sprockets 31-35 when carriage 122 is in the threading
position. It can be appreciated that drive chain 40 would drop away
from the first set of drive sprockets 31-35 during threading if
they were coaxially mounted with the first set of drive rolls
12-16, as they are in the FIG. 1 embodiment.
Each of the first set of drive sprockets 31-35 is operatively
connected to its respective web roll 12-16 by auxiliary drive means
provided by auxiliary drive chains 50-54 engaging respective pairs
of auxiliary drive sprockets 55 and 56, 57 and 58, 59 and 60, 61
and 62, and 63 and 64. It is not necessary for auxiliary drive
sprockets 55-64 to have the same sizes as the first set of drive
sprockets 31-35, but the two sprockets of each matching pair (55
and 56, 57 and 58, 59 and 60, 61 and 62, and 63 and 64) should be
of equal size so that each web roll 12-16 is driven at the same
surface speed as its respective drive sprocket 31-35. Although the
first set of drive sprockets 31-35 has been illustrated as being
positioned below its respective web rolls (the first set 12-16), it
should be recognized that other arrangements are possible. For
example, each of the second set of drive sprockets 36-39 could be
positioned above its respective web rolls (the second set 18-21)
with interconnecting auxiliary drive means similar to that
illustrated for the first set. It is only necessary for each drive
sprocket connected to one set of the web rolls to be in a position
not passed by the web rolls in the other set when the web rolls are
moved into the threading position, to assure that drive chain 40
remains engaged with the drive sprocket.
FIG. 5 illustrates another embodiment of the invention in which the
web rolls in each set are positioned in tiers to permit a greater
accumulation of the web for the same size accumulator. FIG. 5 only
illustrates the arrangement of the web rolls, the drive sprockets,
the take-up sprockets, and the carriage since all other parts could
be similar to those illustrated in FIGS. 1 and 2. In this
arrangement, the first set of web rolls are provided by rolls 65-73
rotatably mounted at the bottom of the frame of the accumulator in
three tiers of three rolls each. In similar fashion, the second set
of web rolls 74-79 are mounted in three tiers of two rolls each on
carriage 222. The web rolls in each tier are larger than the web
rolls in the adjacent tier closest to the opposing set of web rolls
for permitting web 24 and drive chain 40 to be looped from set to
set without interfering with other loops. Web rolls 67 and 70 in
the first set of web rolls 65-73 are employed only for alignment of
web 24 and drive chain 40 and are not functional web rolls for
festooning. Operatively connected to each web roll 65-79 is a drive
sprocket 80-94 with a pitch diameter equal to the surface diameter
of its respective web roll 65-79.
In similar fashion to the other embodiments of the invention, the
accumulator of FIG. 5 includes take-up sprockets in a first set
95-103 rotatably mounted at the top of the accumulator frame and a
second set of take-up sprockets 104-109 rotatably mounted on
carriage 222. The take-up sprockets 95-109 are mounted in a
mirrored relationship to the drive sprockets 80-94. Endless drive
chain 40 is threaded about drive sprockets 80-94 in the same manner
that the web 24 is threaded about web rolls 65-79. Drive chain 40
then continues up to take-up sprockets 95-109 and loops about them
in a mirrored relationship to its path about drive sprockets
80-94.
Having described the preferred embodiments of the invention, it
should be recognized that many variations can be employed within
the scope of the invention. For example, many forms of flexible
drive belt can be used in the invention, a chain being described
only as a preferable form. Likewise, other forms of drive pulleys
which are compatible with the form of drive belt can be employed,
sprockets having been described for use with a chain.
A preferred form of the invention, as described above, includes
take-up sprockets positioned in a mirrored relationship to the
drive sprockets and about which the endless, flexible drive belt
festoons. Mirrored relationship for the invention means that each
drive pulley has a corresponding take-up pulley positioned in the
same relative position at the opposite part of the accumulator. The
importance of the mirrored relationship is that the number of drive
belt loops from the carriage to the fixed set of drive pulleys is
equal to the number from the carriage to the fixed set of take-up
pulleys. Thus, the carriage will be permitted to move in a
direction at the same speed it is pulled in that direction. The
relative sizes of the take-up pulleys is not critical, since they
each rotate freely.
The mirrored relationship arrangement conveniently accomplishes two
beneficial results. It takes up and lets out portions of the drive
belt to correspond to the increasing or decreasing length of the
drive belt festooned about the drive sprockets and it pulls the
second set of web rolls away from the first set of web rolls when
the accumulator is accumulating a reserve portion of web. However,
it should be recognized that other forms of drive belt take-up
means could accomplish these same results, although perhaps not as
conveniently. For example, a single, movably mounted pulley biased
in a direction to take up increasing belt length could be used in
combination with biasing means such as springs or weights.
Furthermore, even when the drive belt take-up means are provided by
take-up sprockets positioned in a mirrored relationship to the
drive sprockets, the second set of take-up sprockets mounted on the
carriage does not have to be mounted away from the second set of
drive sprockets mounted on the carriage. When each of the second
set of take-up sprockets and its respective drive sprocket are of
the second set are chosen to be of equal size they could be
coaxially mounted to the same shaft, since they will be driven in
the same direction at the same speed. However, where the flexible
drive belt is provided by a chain, it is advantageous to mount the
second set of take-up sprockets above the second set of drive
sprockets and in the same plane, since chains are generally
flexible in only one plane.
It should also be recognized that in the broadest sense the
invention does not require a single carriage upon which all of the
web rolls in the second set are mounted. Each web roll could be
independently mounted, although equal movement of each of the
second set of web rolls towards or away from the first set of web
rolls can be most easily assured by mounting all of the second set
of web rolls on a common carriage, as illustrated in the
drawings.
The invention has been described in its preferred forms which
provide several novel features, each of which are quite
advantageous alone and particularly so when used in combination
with each other. Those features are described in the following
claims.
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